1. Field of the Invention
The present invention relates to a semiconductor device including an integrated circuit.
2. Description of the Related Art
One of major causes of defects in integrated circuits is damage of semiconductor elements, electrodes, or the like due to electrostatic discharge (ESD). Thus, in order to prevent damage of an integrated circuit due to ESD, a protection circuit is inserted between a power supply terminal and a connection terminal for connection to an external circuit, and the integrated circuit. A protection circuit refers to a circuit for preventing the supply of overvoltage or overcurrent generated due to ESD to an integrated circuit. Typical examples of elements used for protection circuits are resistors, capacitors, diodes, and the like (see Reference 1: Japanese Published Patent Application No. 2001-339051 and Reference 2: Japanese Published Patent Application No. S63-027044).
For example, Reference 1 discloses a technique by which a resistor is formed by inserting a polysilicon film between two adjacent input-output terminals and a capacitor is formed by overlapping one of the input-output terminals and an end portion of the polysilicon film with a gate insulating film interposed therebetween. Further, Reference 1 discloses a technique by which a diode formed using a polysilicon film is inserted between two adjacent input-output terminals, and a capacitor is formed by overlapping one of the input-output terminals and an end portion of the polysilicon film.
In Reference 2, a wiring formed using a polycrystalline silicon film is inserted between a bonding pad and a transistor in a first stage of an internal circuit as a resistor. In Reference 2, in order to prevent short-circuit between the polycrystalline silicon film and a semiconductor substrate due to ESD, a conductive layer which is in an electrically floating state is provided between the polycrystalline silicon film and the semiconductor substrate.